There were a couple of small PM draft issues that I discovered on 1.1.6 and fixed them. The short of it is that PM drafts (should you have them enabled) would not clear on send, and on initial save would create two copies ... so you ended up with a bit of a log of them.
Fixes are here for those that need them:
https://github.com/Spuds/Elkarte/commit/bee0ad012b02b35a5b2a771cb40db1fc3fc62f28